Electrical control unit



June 1941 N. c. SCHELLENGER ELECTRICAL CONTROL UNIT Filed April 6, 1959r 7 5 w 2 mg n mm 7 mi m v I A Z hw W Patented June 10, 1941 UNITED STPTNT QFFIQE ELECTRICAL CONTROL UNIT Application April 6, 1939, SerialNo. 266,244

8 Claims.

This invention relates to a new and improved electrical control unit andmore particularly to a construction of such units in which the parts ofthe unit are held in assembled relation with a minimum number of parts.

Units of this character, such as variable resistances alone orassociated with switches or separate switches, are made in largequantities at low cost for use in radio receivers, test instruments,public address systems and the like. Their use requires them to becompact and eiiicient in that they must operate uniformly for manycycles of operation. In View of the commercial requirements for smallsize and low cost, it is important to eliminate all extra parts and tohold the necessary forming and assembling operations to a minimum.

It is an object of the present invention to provide a new and improvedelectrical control unit assembly.

It is a further object to provide such an as sembly comprising a rotaryshaft and a shaft bearing in which the shaft bearing is removably heldin place relative to the body of the unit.

It is an additional object to provide an assembly of this character inwhich a single operation serves to secure a housing to the body of theunit and also to secure in place the shaft bearing.

It is also an object to provide a construction in which a groundingplate serves as means for seclning a shaft bearing to a base of a unit.

It is a further object to provide an assembly in which the housingsecuring means jointly serve to secure the shaft bearing and groundingplate in position and to fix the parts in such manner as to preventrelative rotation.

It is an additional object to provide a unit assembly which may bedisassembled without the destruction of major elements of the assembly.

It is another object to provide an assembly which is simple in designand composed of but few parts and is adapted for commercial productionand use.

Other and further objects will appear as the description proceeds.

I have shown certain preferred embodiments of my invention in theaccompanying drawing, in which Figure 1 is a face view of the assemblywith the cover cut away to show the interior construction;

Figure 2 is a section, partly broken away, on line 2-2 of Figure 1;

Figure 3 is a view of the construction as seen from below the base; and

Figure 4 is a section partly broken away, taken on line 4-4 of Figure 3.

In the drawing, the base H is preferably formed of non-conductingmaterials, such as sheet synthetic resin or the like. This base H isprovided with a lateral extension l2. The inner face of the base llcarries the resistance strip l3 having the ends I4 and I5 held to thelateral extension !2 of the base by the rivets I6 and H, which rivetsalso serve to hold the terminals l8 and I9 in position. The base II isprovided with the central opening through which extends a locating andbearing portion 2! of a thimble 22. This thimble 22 is provided with acentral opening 23 which serves as a bearing for the shaft 24. The innerend of the shaft 2 1 has a drive plate 25 and a stop plate 26 securedthereto by deforming the inner end 21 of a reduced extension on theshaft. The drive plate 25 is formed of nonconducting material and drivesthe movable contact member 28 which engages the resistance strip !3. Thecollector ring 29, which is engaged by a portion of member 28, isprovided with an integral terminal and extension portion 39 fitted inthe opening 3! in the base l i.

The thimble 22 is provided with a laterally eX- tending shoulder 32which engages the outer face of the base H. This shoulder 32 hasoppositely located notches 33 formed therein, these notches beingutilized to hold the thimble against rotation. The ground plate 34 has araised portion 35 which fits over the shoulders 32 of the thimble andhas locating portions 36 which fit within the notches 33 of the shoulder32 on the thimble to maintain the thimble and plate against relativerotation. The ground plate 34 may be provided, as shown, with upstandinglugs 3'! which serve to engage openings or notches in any suitablesupport such as -a radio chassis, and thus prevent the entire assemblyfrom rotation relative to its support.

In the form of construction shown, the base I I is provided with anadditional lateral extension 38 to receive a tap extension 39 of theresistance strip [3. This tap extension is held in place by the rivet 40which also holds the connecting lug or terminal 4! in position: Theground plate 34 is provided with recesses 42 and 43 which provide ampleclearance between the metal of the ground plate and the rivet holdingthe connecting lug to the tap extension. It will be understood that boththe cutaway portions 42 and 43 are provided so that the plate may bestandardized and used with tap extensions in either relative positionThe plate 34 is further provided with shoulders 44 and @5 which, withthe plate in proper assembled relation on the base, are located adjacentand spaced from the main lateral extension l2 of the base.

The housing 45 is preferably formed of metal and houses the variableresistance parts located upon the inner face of the base II. Thishousing 45 is provided with securing ears 41, 48, 59, 5B and 5! whichare bent over against the under face of the ground plate 34 to securethe cover in place. These ears not only secure the parts together butserve to ground the metal cover to the ground plate so that a fullygrounded shield is provided for the entire assembly. It will be notedthat the ears 5% and 5| are so proportioned as to fit snugly between theshoulders M and 45, respectively, and the adjacent sides of the lateralextension I2 of the base. By this fit the plate 34 is definitely locatedrelative to the base and is positively prevented from rotating relativeto the base.

It will be apparent that the construction shown serves to connect all ofthe several elements going to make up the electrical control unit shown,without the necessity for rivets or other securing means insofar as thehousing, grounding plate and bearing thimble are concerned. Inassemblingthe parts after the resistance strip has been riveted to thebase,'the thimble 22 may beinserted in the opening 29 in the base. Theinsulating washer '52 is fitted against the inner face of the base Ifaround the bearing portion 2| of the thimble, and the collector ring 29and its associated terminal are next put in place. The shaft M, alreadyprovided with the drive plate, variable contact and stop plate, isinserted through the thimble 21 from the inner face of the base. Thisportion of the assembly is then held in place by inserting the G-washer53 in the groove 5 in the shaft 24. The ground plate 3 3 is nextslippedover the thimble and the portions it properly seated in the notches 33in the shoulder E2 of the thimble. With the plate, and consequently thethimble, turned to the proper relative rotary position, the housing isslipped over the inner face of the base, enclosing the parts, and theears i? to 52 are bent over against the outer face of the ground plate,completing the assembly.

While the unit assembly has been shown as directed to a variableresistance, it will be apparent that it may be applied to a variableresistance having a switch mounted upon its housing for joint operationtherewith. It may also be used with other electrical control unitsmounted upon the base and enclosed within the housing, such for example,as switches alone. The unit may be disassembled by bending back thesecuring ears and by removing the C-washer holding the shaft in place.This makes it possible to salvage major portions of defective units 7which is not true when the thimble and ground plate are permanentlysecured in place as in usual constructions.

Besides the several features noted above, the present invention has afurther very important inherent advantage. In the light of thecontinually growing demand for smaller controls, the conventionalrivet-like manner of securing the bushing or bearing thimble to theinsulated base has been found objectionable. It necessitated thepresence of a shoulder or flange on the inner end of the bushing toengage over the inner face of the insulated wall. The grounded bushingwas thus exposed to the control instrumentalities and as aconsequence-special provision had to be made for adequate electricalclearance. This required space.

'In the present invention, no part of the grounded bushing is exposed atthe inside of the control; and this desirable result is obtained tivemanner of locating or centering the bushing on the base in conjunctionwith the rigidity 'of its securement brought about by clamping themedial flange of the bushing between the base and the grounding plate isresponsible for the attainment of this desideratum.

The centering or locating end portion of the I bushing, serving only as'a dowel pin, i. e., to hold the bushing properly centered on the base,need not pass entirely through the aligned holes in the base and spacingwasher, and preferably terminates short of the inner face of theinsulated wall formed jointly by the base and spacing washer. Thepresence of the bushing, therefore, need not be considered from thestandpoint of electrical clearance.

The optimum of compactness and accuracy of alignment is thusachievedwithout sacrifice of rigidity and with the advantage'ofsimplified less expensive assembly.

I have shown certain preferred embodiments of my invention byway ofexample, but it is capable of modification and change-to meet varyingconditions and requirements and I contemplate such variations as'comewithin the spirit and scope of the appended claims.

What is claimed is:

1. In an electrical control unit assembly, abase having an openingtherein, a separate shaft bearing thimble having a portion engaging oneface of the base and having its bore in line with the opening in thebase, control mechanism upon the opposite face of the base, a shaftoperatively connected to said mechanism and extending'through the boreof the thimble, the base having a lateral extension thereon, a plate onthe thimble side of the base having portions overlying portions of thethimble, shoulders on the plate adjacent to the lateral extension of thebase, and a housing upon the opposite side of the base, said housinghaving ears extending beyond the base and engaging the plate to maintainthe members in assembled relation, certain of the ears inter'fittingwith the lateral extension of the base and the shoulders on theplate toprevent relative rotation of the parts. v

'2. In a variable resistance unit,"a non-conducting base having acentral opening therein and having a lateral extension thereon, aresistance strip secured to the inner face of the basehaving terminalsupon the lateral extension of the base, a separate thimble upon theouter faceof the base, said thimble having its bore in line with'theopening in the base and having a locating and bearing portion within theopening'in the base, said thimble having an extended shoulder, upon theouter face of the base, a notch in saidshoulder, a shaft extendingthrough the hereof the thimble, movable contact means carried: by theinner end of the shaft engaging the resitance strip, a ground plate uponthe outer face'of the base, said plate having a portion overlying theshoulder of the thimble to hold the thimble against the base and havinga portion fitting into the notch of the thimble shoulder to preventrelative rotation between the thimble and plate, the plate havingshoulders adjacent to the lateral extension of the base, a housingcovering the inner face of the base, said housing having securing earsextending beyond the base and engaging the plate to maintain the partsin assembled relation, certain of said ears engaging the shoulders onthe plate and the extension on the base to maintain the parts fixedagainst relative rotation.

3. In an electrical control unit having a rotatable operating shaft, abushing providing a bearing for the shaft and having a flange mediallyof its ends, a base having a hole receiving one end portion of saidbushing and having the outer face thereof engaging the adjacent side ofthe flange, said entire end portion being no larger in diameter than thehole, control mechanism adjacent to the inner face of the base, a metalgrounding plate fitted over the opposite end portion of the bushing andengaging the flange so that the flange lies between the grounding plateand the base, said grounding plate having portions extending outwardlyfrom the periphery of the flange and lying adjacent to the periphery ofthe base, a housing for said control mechanism having an open endthereof closed by the base, means on the housing engaging the base andsupporting the base against movement into the housing, and ears on saidhousing having portions bent over the outer face of the grounding plateto clamp the base and the grounding plate to the housing with the flangeof the bushing clamped between the plate and the base to thus establishgood electrical contact between the bushing and the grounding plate.

4. In an electrical control unit having instrumentalities controlled byan operating shaft, a metal housing for the instrumentalities having anopen end, a wall of insulating material closing said open end of thehousing and supported against movement into the housing, said wallhaving a hole through which the operating shaft passes, a metal bushingseated on the outer face of the wall and providing a bearing for theshaft, readily separable interengaging means on the bushing and wall forholding the bushing against shifting laterally from its position atwhich the shaft is properly aligned with the control instrumentalities,means on the bushing providing a laterally projecting shoulder spacedoutwardly from the adjacent portion of the wall, a metal grounding plateoverlying the outer face of the wall and having a part engaging saidshoulder, a metal to metal connection between the housing and groundingplate by which the grounding plate is drawn toward the wall to clamp thebushing against the outer face of the wall and whereby the bushing,grounding plate, and metal housing are electrically connected, and meansfor preventing relative rotation between the bushing and groundingplate.

5. In an electrical control unit having an operating shaft, a wall ofinsulating material, said wall having a hole through which the shaftpasses, a bushing providing a bearing for the shaft, one end portion ofthe bushing providing a centering projection fitted in the hole, no partof the centering projection being larger than the hole, a flange on thebushing engaging one side of the wall, control instrumentalities at theother side of the Wall, a metal plate having a portion engaging theouter face of the flange, a housing covering the controlinstrumentalities and closed by the wall, means on the side of thehousing extending beyond the wall and over the metal plate to draw theplate toward the housing and thereby clamp the bushing to the wall andsecure the wall to the housing, and interengaging means on the bushingand plate for holding the same against relative rotation.

6. In an electrical control unit having an operating shaft, a base ofinsulating material having a hole through which the shaft passes, abushing providing a bearing for the shaft, a centering projection on thebushing fitting in said hole, no portion of said centering projectionhaving a diameter larger than that of the hole, a shoulder on thebushing projecting laterally out from the centering projection to engagethe outer face of the base and support the bushing against inwardmovement, a second shoulder on the bushing spaced axially outwardly fromthe first named shoulder, an apertured plate fitted over the outer endof the bushing and bearing against said second shoulder, said plateoverlying the outer face of the base, a cover for the control unitengaged over the inner face of the base, and means connecting anddrawing the cover and plate together to thereby clamp the shoulderedportion of the bushing between the plate and the base and also clamp thebase between the plate and cover.

7. In an electrical control unit of the character described, a housingfor the instrumentalities of the control, a wall of insulating materialclosing one end of the housing and providing a base for the controlinstrumentalities, said wall having a hole therethrough, an operatingshaft entering the housing through said hole, a bushing providing abearing for the shaft, a projection on the bushing fitted in the hole tocenter the bushing and hold the shaft in proper alignment with thecontrol instrumentalities, said centering projection being no longerthan the total length of the hole in the wall, means for supporting thebushing on the exterior of the wall against inward axial movement, 50that no part of the bushing is exposed to the control instrumentalities,a shoulder on the bushing exteriorly of the wall, an apertured platefitting over the outer projecting end portion of the bushing and restingagainst said shoulder, and means connecting the plate and the housing ina manner clamping the wall between the housing and plate and confiningthe shouldered portion of the bushing between the plate and the wall.

8. In an electrical control unit assembly, a base having an openingtherein, a separate shaft bearing thimble having a portion engaging oneside of the base and having its bore in line with the opening in thebase, control mechanism at the opposite side of the base, a shaftoperatively connected with said mechanism and extending through the boreof the thimble, a shoulder projecting laterally from the thimbleadjacent to the base, said shoulder having a notch therein, a metalgrounding plate having a portion fitting over said shoulder, a portionengaging the notch in the shoulder for preventing relative rotationbetween the plate and the thimble, and a portion overlying the majorpart of the base, a metal housing covering the mechanism, and earsintegralwith the side Wall of the metal housing extending beyond thebase and bent over the grounding plate to clamp the thimble between theplate and the base.

NEWTON C. SCIIELLENGER.

